London could one day rival Pisa in the leaning tower stakes after surveyors found that the capital city’s famous tower rising above the U.K. Parliament has developed a visible tilt.

But Brits won’t be heralding The Leaning Tower of London any time soon. According to the Telegraph, engineers estimate that at the present rate it would take some 4,000 years to match the angle on the famous Italian structure.

Apparently the clock tower at the Palace of Westminster complex – commonly referred to as Big Ben, which is the name of the bell inside – is sinking into the ground. The tilt is occurring because the structure is settling into land on the north side quicker than elsewhere. Investigators blame the movement on decades of building work in and around the 315-ft. tall tower, built in 1858.

Bizarrely, a recently published 2009 report on its conditions noted a mysterious “event” in the 10 months between Nov. 2002 and Aug. 2003 that caused the tower to lurch several millimeters. No single known factor can fully explain the development.

The lean is reportedly already causing cracks in the walls of other parts of the House of Commons, which sits beneath Big Ben. John Burland, emeritus professor and senior research investigator at Imperial College London who has worked on the Big Ben tower and in Pisa, calmed any fears.

“If it started greater acceleration, we would have to look at doing something but I don’t think we need to do anything for a few years yet,” he told the Telegraph.

Joe Jackson is a contributor at TIME. Find him on Twitter at @joejackson. You can also continue the discussion on TIME’s Facebook page and on Twitter at @TIME.